TY - JOUR
T1 - Transcriptional responses to ionizing radiation reveal that p53R2 protects against radiation-induced mutagenesis in human lymphoblastoid cells
AU - Tsai, M. H.
AU - Chen, X.
AU - Chandramouli, G. V.R.
AU - Chen, Y.
AU - Yan, H.
AU - Zhao, S.
AU - Keng, P.
AU - Liber, H. L.
AU - Coleman, C. N.
AU - Mitchell, J. B.
AU - Chuang, E. Y.
N1 - Funding Information:
1Radiation Biology and Oncology Branches, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; 2Advanced Technology Center, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; 3Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA; 4Radiation Oncology, School of Medicine and Dentistry, University of Rochester, Rochester, New York, USA; 5Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA and 6Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan
PY - 2006/1/26
Y1 - 2006/1/26
N2 - The p53 protein has been implicated in multiple cellular responses related to DNA damage. Alterations in any of these cellular responses could be related to increased genomic instability. Our previous study has shown that mutations in p53 lead to hypermutability to ionizing radiation. To investigate further how p53 is involved in regulating mutational processes, we used 8K cDNA microarrays to compare the patterns of gene expression among three closely related human cell lines with different p53 status including TK6 (wild-type p53), NH32 (p53-null), and WTK1 (mutant p53). Total RNA samples were collected at 1, 3, 6, 9, and 24 h after 10 Gy γ-irradiation. Template-based clustering analysis of the gene expression over the time course showed that 464 genes are either up or downregulated by at least twofold following radiation treatment. In addition, cluster analyses of gene expression profiles among these three cell lines revealed distinct patterns. In TK6, 165 genes were upregulated, while 36 genes were downregulated. In contrast, in WTK1 75 genes were upregulated and 12 genes were downregulated. In NH32, only 54 genes were upregulated. Furthermore, we found several genes associated with DNA repair namely p53R2, DDB2, XPC, PCNA, BTG2, and MSH2 that were highly induced in TK6 compared to WTK1 and NH32. p53R2, which is regulated by the tumor suppressor p53, is a small subunit of ribonucleotide reductase. To determine whether it is involved in radiation-induced mutagenesis, p53R2 protein was inhibited by siRNA in TK6 cells and followed by 2 Gy radiation. The background mutation frequencies at the TK locus of siRNA-transfected TK6 cells were about three times higher than those seen in TK6 cells. The mutation frequencies of siRNA-transfected TK6 cells after 2 Gy radiation were significantly higher than the irradiated TK6 cells without p53R2 knock down. These results indicate that p53R2 was induced by p53 protein and is involved in protecting against radiation-induced mutagenesis.
AB - The p53 protein has been implicated in multiple cellular responses related to DNA damage. Alterations in any of these cellular responses could be related to increased genomic instability. Our previous study has shown that mutations in p53 lead to hypermutability to ionizing radiation. To investigate further how p53 is involved in regulating mutational processes, we used 8K cDNA microarrays to compare the patterns of gene expression among three closely related human cell lines with different p53 status including TK6 (wild-type p53), NH32 (p53-null), and WTK1 (mutant p53). Total RNA samples were collected at 1, 3, 6, 9, and 24 h after 10 Gy γ-irradiation. Template-based clustering analysis of the gene expression over the time course showed that 464 genes are either up or downregulated by at least twofold following radiation treatment. In addition, cluster analyses of gene expression profiles among these three cell lines revealed distinct patterns. In TK6, 165 genes were upregulated, while 36 genes were downregulated. In contrast, in WTK1 75 genes were upregulated and 12 genes were downregulated. In NH32, only 54 genes were upregulated. Furthermore, we found several genes associated with DNA repair namely p53R2, DDB2, XPC, PCNA, BTG2, and MSH2 that were highly induced in TK6 compared to WTK1 and NH32. p53R2, which is regulated by the tumor suppressor p53, is a small subunit of ribonucleotide reductase. To determine whether it is involved in radiation-induced mutagenesis, p53R2 protein was inhibited by siRNA in TK6 cells and followed by 2 Gy radiation. The background mutation frequencies at the TK locus of siRNA-transfected TK6 cells were about three times higher than those seen in TK6 cells. The mutation frequencies of siRNA-transfected TK6 cells after 2 Gy radiation were significantly higher than the irradiated TK6 cells without p53R2 knock down. These results indicate that p53R2 was induced by p53 protein and is involved in protecting against radiation-induced mutagenesis.
KW - Microarray
KW - Radiation
KW - TK6
KW - p53R2
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UR - http://www.scopus.com/inward/citedby.url?scp=31544442476&partnerID=8YFLogxK
U2 - 10.1038/sj.onc.1209082
DO - 10.1038/sj.onc.1209082
M3 - Article
C2 - 16247478
AN - SCOPUS:31544442476
SN - 0950-9232
VL - 25
SP - 622
EP - 632
JO - Oncogene
JF - Oncogene
IS - 4
ER -